A case report of monochorionic diamniotic twin pregnancy complicated by velamentous placenta and vasa previa

This study reported a case of an elderly primipara with a scarred uterus who had a monochorionic diamniotic twin pregnancy, complicated concurrently by velamentous placenta and vasa previa, which represents an extremely rare and high-risk obstetric composite complication. Velamentous placenta refers to the condition where the umbilical cord attaches to the fetal membranes rather than the placental substance, with umbilical vessels traversing through the amniotic-chorionic space to reach the placenta. Its incidence in monochorionic twin pregnancies is significantly higher than that in singleton pregnancies. When combined with vasa previa, where fetal vessels without Wharton's jelly protection cross or are adjacent to the internal cervical os and lie beneath the presenting part, it is highly prone to causing acute fetal hemorrhage due to membrane rupture, leading to catastrophic perinatal outcomes. In this case, through multidisciplinary collaboration, rigorous prenatal monitoring, and individualized selection of the delivery timing, maternal and neonatal safety was successfully achieved.